In electronic controls such as automotive radios and the like, control knobs or buttons bearing graphics such as letters, numbers and other symbols are often illuminated to make the graphics easily visible. An inexpensive method of making such buttons of good quality is by a two part molding process. A first shot of translucent material is injected into a mold to form a base part containing a raised symbol. A second shot of opaque material is injected to surround the symbol. The resulting button when back lighted will have the raised symbol illuminated and the remainder of the button will be dark due to the layer of opaque material.
Some symbols such as A, B and D are closed figures which define inner islands containing opaque material separate from the remainder of the button surrounding the graphic. The opaque material is fed to the island during the second shot by a bridge behind a portion of the raised symbol which connects the island with the area surrounding the symbol. Heretofore, this has resulted in the button typified by that shown in FIGS. 1, 2, 3 and 4. A button 10 bears the letter "A" having two angled side legs 14 and a cross bar 16 to define an island 18 which is isolated from the outer region 19 of the button outside the legs and crossbar. The base 20 of the button 10, shown in FIG. 2, is a cup-shaped element made of translucent material. The base has a front base surface 22 carrying a ridge 24 shaped to form the letter "A" which extends from the front base surface 22 to the front button surface 26. The inner wall of the button comprises a rear base surface 28. A lamp 30 mounted on a circuit board 32 or other light source behind the button illuminates the rear base surface so that the letter "A" is illuminated. An aperture 34 in the base extends transverse to and underneath the crossbar 16. To provide contrast and to suppress light through the front of the button other than through the illuminated symbol, an opaque part 36 is added to the button by injection molding so that the two parts together form a smooth uninterrupted front button surface 26. The opaque material during molding surrounds the letter "A" and flows through the aperture 34 to fill the island 18. The resulting opaque bridge 38 filling the aperture 34 impedes the flow of light to the portion of the crossbar 16 adjacent the bridge thereby causing a shadow on the light bar which is aesthetically objectionable.